Heat exchange between the body and the environment is affected by a wearer's clothing, which can limit convective and evaporative cooling. One solution to this problem is to incorporate a ventilation system within the clothing which encourages cooling. Ventilation can occur when air moves through the fabric itself, through clothing openings such as the neck, closures, and arm openings, and through vents strategically placed in the clothing to maximize airflow.
When performing physical work, a wearer's body generally produces excess heat. This increased heat production is diminished in part while the work is being performed due to motion-induced wind and increased convection inside a garment. This effect, however, cannot compensate entirely for increases in body heat produced during activity. Modification of the wearer's garment in such as way as to reduce both excess body and environmental heat facilitates both comfort and job performance.
In industries involving biological, chemical, or physical hazards, special protective clothing must be worn as a barrier to shield wearers from physical harm. Such protective clothing, however, may present another hazard by reducing a wearer's ability to dissipate heat through sweat evaporation. The combination of physical stress, environmental heat, and additional protective layers of clothing may cause an excessive level of heat stress to a wearer, which is both physically dangerous for the wearer and may, at a minimum, cause reduced physical work performance.
In addition to physical stress and environmental heat, electrical industry workers can be exposed to electrical arc flashes, which include radiant energy, convective energy, and conductive energy, with potential to cause severe injury. Burns resulting in death or requiring lengthy rehabilitation have occurred when workers have been exposed to an electrical arc. Many of these burns have been further complicated by ignition, melting and continued burning of non-flame resistant materials or non-arc resistant materials.
Utility maintenance workers, such as linemen, are subject to sudden intense electrical arc flashes and are required to wear flame-resistant clothing, including flame-resistant shirts, in an attempt to protect themselves from these hazards. Most flame-resistant shirts are made of relatively heavy, impermeable fabric and cause retention of body heat. Heat stress and perspiration can increase these risks to the wearer.
Other efforts to address these problems have involved lightweight fabrics made from exotic blends of fibers including aramid and carbonized fibers. These fabrics are costly, and while lighter weight, offer a lesser degree of protection, exist in limited color selections, and may degrade more readily in sunlight and ultraviolet rays than comparable grades of more common flame-resistant fabrics. It is also common in the electrical industry to layer two shirts with the heaviest, flame-resistant shirt on top, in order to combat moisture buildup from perspiration. This solution, however, also leads to the accumulation of excessive body heat because the moisture level of the inner air gap between the two layers becomes saturated and unable to support further evaporative cooling.
Vented shirts are known in the art, but conventional vented shirt designs are usually not compatible with flame-resistant requirements. For example, the vented shirt described in U.S. Pat. No. 4,608,715 incorporates a zippered side vent near each sleeve seam. When a zipper is opened, a series of vent holes is exposed and allows radiant heat of an arc to pass directly through the vent and holes to the wearer.
This conventional vent design and many others are not suitable for wearers who are subjected to sudden, intense electrical arc flashes because zippers, rivets, snaps, eyelets and other closures may subject a wearer to burns and other injury. They also can conduct heat and electricity and provide a route through a protective garment by which heat and electricity may pass. Further, mesh or webbing incorporated into the venting of conventional designs was not flame resistant, and would melt and cause injury upon exposure to an electrical arc. Also, conventional meshes are characteristically flat and open, leaving skin poorly covered and thus potentially exposed to heat and burns during an electrical arc flash. This makes the construction of a flame-resistant, ventilated shirt particularly challenging. The incorporation of specialty flame-resistant zippers, for example, is prohibitively expensive. Likewise, the incorporation of other specialty flame-resistant closures, like hook and loop material, are not only expensive, but cause damage to mesh and other fabric, and lose their ability to properly close over time. Damage to the fabric caused by closure notions can lead to increased hazards to a wearer.
Front venting of flame-resistant shirts further presents the problem of snagging as a worker climbs and grapples in the course of performing his or her job, and may potentially create a direct linear path along which harmful electrical arcs can travel from the environment, through the garment, to the wearer. For all the foregoing reasons, the end product of these approaches results in shirts that are less protective (even dangerous), more expensive, and undesirable in appearance compared to a conventional shirt.
The present invention addresses these problems by using readily available, moderately priced flame-resistant fabrics and unique construction techniques. The unique construction comprises several elements, namely a standard front half, but incorporating a side or back-caped vent (or both). One embodiment includes strategically positioned ventilation eyelets to increase air flow without diminishing protection. These unique features achieve greater ventilation while being constructed in a manner and of materials to ensure compliance with applicable standards and regulations (ASTM F1506, NFPA 70E, and the apparel requirements of 29 CFR 1910.269). The front half of the shirt is made using a flame-resistant fabric with a standard design, and does not have to be specially made, which reduces the total cost of manufacturing.
The back half of the shirt incorporates vent openings which are uniquely made and located so that the wearer is not exposed to radiant heat through the openings in the event of an electrical arc exposure that is within the arc-rated capacity of the shirt. A ventilating panel made from a fabric which allows the circulation of air, like a mesh, knit, or moisture-wicking material, allows maximum air circulation through the vents while providing increased protection to a wearer from electrical arc flashes. Prior art shirt constructions with “ventilated panels” typically incorporated open-holed or very loosely knit, “two-dimensional” (flat) nylon or polyester mesh, through which the radiant energy of an electrical arc might pass, and which are unsafe in the electrical industry. Further, shirt constructions which would allow mesh, knit, or other ventilated panels to be visible from the outside of the shirt are typically not safe in environments with electrical arc exposures.
In one embodiment of the present invention, the ventilating panel is constructed from a mesh knit. Ideally, the mesh knit is dimensional (not flat) so that holes in the mesh appear to be open when viewed from the front, but from a side view, the holes appear to be somewhat, or completely, closed. The mesh knit is flame-resistant to provide additional protection to a wearer. For example, flame-resistant meta-aramid material or material exhibiting similar construction and flame-resistant properties may be used. Advantageously, a mesh knit in accordance with the present invention can shield the body of a wearer, and any non-flame-resistant undershirt or undergarments of the wearer, from the harmful effects of radiant and convective heat radiation of an electrical arc exposure.
In another embodiment of the present invention, the ventilating panel is constructed from a lightweight or a midweight knit fabric. The lightweight or midweight knit fabric can have moisture-wicking properties. This embodiment is ideal for wearers who desire a solid ventilating panel rather than a panel containing mesh “holes.” Lightweight or midweight moisture-wicking knit fabrics are available with flame-resistant qualities to provide additional protection to a wearer.
In yet another embodiment of the present invention, the ventilating panel is constructed from heavyweight knit fabric for vent protection plus additional wearer protection from layering. This embodiment of the vented, flame-resistant shirt is able to withstand greater exposures to which the shirt may be subjected, and is ideal for a wearer working in more hazardous situations. Flame-resistant fabrics, such as those made with modacrylic fibers, can be chosen depending upon the desired durability, performance, and ability to extinguish flames. Heavyweight moisture-wicking knit fabrics are also available with flame-resistant qualities to provide additional protection to a wearer.
In still other embodiments of the present invention, the ventilating panel can comprise, but is not limited to, blended or unblended flame-resistant fabrics, including generic flame-resistant tricot warp knit mesh made from blends such as carbonized, modacrylic fibers, para-meta- or other aramid fibers, or flame-resistant treated natural fibers. Some level of non-flame-resistant fiber may be incorporated into an embodiment of the present invention, so long as the fabric would ultimately be flame-resistant. Examples of some suitable fabrics include NOMEX®, DRIFIRE® Tubular jersey knit, and INDURA® ULTRASOFT®, TECGEN®, TWARON®, PROTEX®, and KEVLAR®. Moisture wicking properties can add an additional element of comfort for a wearer.
It is therefore the object of the present invention to provide a flame-resistant shirt that uses readily available flame-resistant fabrics, has a standard front half, and a vented back half, which provides ventilation without compromising the flame-resistant quality.
These features, and other features and advantages of the present invention will become more apparent to those of ordinary skill in the relevant art when the following detailed description of the preferred embodiments is read in conjunction with the appended drawings in which like reference numerals represent like components throughout the several views.